STEPS OF CONSTRUCTION
(i) Draw a ray OA.
(ii) With O as centre and a conventient radius, draw an arc cutting OA at P.
(iii) With P as centre and the same radius as above, draw an arc, cutting the above arc at Q.
(iv) With Q as centre and the same radius, draw another arc, cutting the arc drawn in Step (ii) at the point R.
(v) With Q and R as centres and the same radius, draw two arcs intersecting each other at M.
(vi) Join OM and produce it to point B.
Then, `angleAOB` is the required angle of measure `90^(@)`.
